


In the Heat of the Moment

by 21K1LLJ0YS



Category: Undertale (Video Game)
Genre: Aftercare, Biting, Breeding, Come Inflation, Dubious Consent, F/M, Gentle Sans, Knotting, Mating Cycles/In Heat, Rape/Non-con Elements, Rough Sex, he didn't mean it
Language: English
Status: Completed
Published: 2018-08-27
Updated: 2018-09-03
Packaged: 2019-07-03 07:09:53
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 3
Words: 7,079
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15813966
Author URL: https://archiveofourown.org/users/21K1LLJ0YS/pseuds/21K1LLJ0YS
Summary: Sans comes home to find his human mate in the middle of her first heat. He doesn't exactly handle it as well as he would have liked to.





	1. Chapter 1

**Author's Note:**

> I want to make it clear that I don't condone rape in any way. Always get your partner's consent before doing anything to them.

When Sans started this day, he didn’t exactly think that it would go like this. He had arrived at his job above ground, which he had been grudgingly going to since the monsters broke the barrier 2 year ago, just like any other day. However, a few hours in, he recieved a text from his little human mate. 

*Sweetheart*- “Sans, I think something’s wrong with me.”

He blinked, confused and a bit worried. What did she mean? 

*Big Bones*- “what’s up, sweetheart? feeling a little bone-ly? ;)” 

There was a pause, where Sans hoped she was giggling like she usually does when he puns.

*Sweetheart*- “No, I think something’s REALLY wrong.”

His eyelights vanished in a flash. She barely ever told him if she got sick, let alone asked for help. Whatever was going on must be really terrible. He couldn’t let anything bad happen to his mate. 

n o t h i n g.

Sans didn’t even bother to let his boss know he was leaving. He just teleported into her apartment, desperate to make sure she was ok. 

The moment he appeared, the scent of her nearly toppled him. He keeled forward, claws grasping at his soul, which was pulsing painfully. 

Heat.

His mate… was in heat. 

What? 

How? 

Humans don’t have heats, so what-.

His soul’s insistent throbbing cut off his train of thought like an angry driver cutting off a grandma. 

That’s it! Their souls! Sans had confessed to his sweetheart that they were soulmates only a month ago, and since then, they had grown even closer, even going so far as to let their souls touch. This must be some weird quirk in their biologies that would cause the human soulmate of a monster to exhibit monster-like cycles. 

He himself had had a few heats since meeting her, but he always stayed far away, extremely conscious of the fact that his little mate was very uncomfortable with that kind of intimacy. 

Oh, he had pushed her at first, thinking that it was just nerves, but when he pulled her into his lap to grind her against him once, his massive size making him feel powerful when compared to her little body, and she burst into tears, he regretted his actions immediately, erection vanishing instantly at the sight of his mate crying. He had held her while she cried, mumbling frantic apologies and soothing coos into her hair. He was barely able to make out what she tried to say, but what he understood made him growl in fury. She’d been raped by a past boyfriend, and now she was absolutely terrified to let someone touch her in an intimate way again. To say that he never pushed her again was an understatement. He made sure that she was comfortable with what he was doing whenever their kissing became heated, or when he came up behind her while she was making something in the kitchen and lazily pinned her against the counter. 

Now, though…

Monster heats were hardly ever dangerous. The first few could be a little rocky, but in general, nobody came out of it with more than some dehydration and sore muscles. 

Human heats were completely uncharted territory, at least from what Sans knew. He’d never even heard of this happening. He knew that humans were strong, but his little mate wasn’t equipped for this kind of thing! 

A terrifying thought gripped him and made his magic flare.

What if this heat killed her? 

And then an even worse thought. 

What if he tried to help her, and THAT killed her?

He shuddered, but his instincts were driving him now, and they were saying that his mate  
N E E D E D him. So, proverbial heart in his throat, Sans climbed the stairs leading to her bedroom, hardly able to stand up straight from the overwhelming scent of her. As he reached her door, he heard little whimpers from the other side, and despite himself, felt his magical member forming thickly in his shorts. He raised a tentative hand and knocked. 

“sweetheart? can i come in?

He waited breathlessly for an answer, needing one more with each passing second as he felt his control slipping. In his mind’s eye, he saw himself ripping the door off its hinges and stalking towards her bed to grab her ankles, so small in his huge hands. He saw himself dragging her to the edge of the bed and towards his obscenely tented shorts, licking a magical tongue across his teeth in delight at the prospect of knotting her and filling her little womb with his thick seed. He couldn’t get her pregnant, he knew that for a fact. Humans and monsters couldn’t work like that. Then again, his mate, his HUMAN mate was in the middle of a heat, so who knows? 

Only a few seconds must have passed, but it felt like an eternity to Sans, who, under the weight of his imaginings, was leaning fully against the door. An exhausted voice sounded from the other side and brought him back to reality. 

“I don’t know if that’s a good idea, Sans.”

He snarled, quickly being taken over by a more bestial side of him. Like hell it wasn’t a good idea. He was her mate, and it was his J O B to take care of her. 

“i’m comin’ in, baby girl. it’ll be ok.”

Trying not to burst in with the massive tent in his shorts in full view, Sans slowly opened the door and peered around it. His breath caught.

His precious little mate was a mess, but stars, she was a H O T M E S S. She was sprawled on her bed, sweat beading on every surface of skin that he could see… which was quite a lot. She wasn’t naked, but she definitely wasn’t dressed for the cold winter weather outside. She was desperately grasping at her sheets as she keened painfully. Sans could tell that she hadn’t been touching herself, because if she had, she wouldn’t have been able to stop. 

Speaking of being unable to stop, Sans practically ran towards her, brain frantically trying to backpedal and keep his distance, body doing the exact opposite. He climbed on top of her, his “big boned” body several times larger than hers, and buried his face into the base of her neck, where that heat scent was coming from strongest.

D E L I C I O U S.

His thick, obcenely long tongue escaped the tight seal that Sans had tried to make with his teeth and laved across her throat, savoring the taste of heat and sweat and drooling red magic on her in the process. 

There was no way he could stop himself from taking her now. Not when she was whining and writhing against him, her soul practically B E G G I N G H I M to soothe the ache in her empty womb. 

With one hand, he gripped the collar of her shirt and ripped the flimsy material off of her, leaving him with the delightful view of his beautiful mate in only her under-things. She moaned, obviously unable to comprehend anything apart from her body’s desperate need for… something. She wasn’t really sure what. Now that her soulmate was so close, cognitive thought was basically out of the question. All she knew was her soul was pleading with his to take care of her. 

With the same eagerness that he removed her shirt, Sans also tore off her bra and underwear, leaving his mate deliciously exposed to his wandering gaze. 

It absolutely didn’t surprise him that she was as gorgeous without clothes on as she was with them, if not more. Hell, she could have been fucking neon yellow under there and he still would have thought she was a treasure. 

However, now was not the time to be savoring ever little bit of skin that was new to be explored by his eager mouth… No… not the time… 

She needed him now. He could feel her skin burning up, far hotter than it should have been, and he knew that he had to act quickly, at least until her heat settled a bit. 

Sans returned to his previous delight of mouthing at her exposed throat while he trailed a bony hand down between her breasts, over her soft abdomen, and lower until he found the little patch of curls that guarded her opening. 

His knuckle bone spread her labia and he felt how painfully, U N B E A R A B L Y wet she was. She was hotter than a furnace, and wetter than a damn aquarium. When he nudged her opening with his knuckle, he could feel her clenching desperately. They didn’t have much time for foreplay, but he needed to prep her, or there was no way that she could take him. 

Slowly, Sans slipped his forefinger into her tight little entrance, groaning at how the walls fluttered around him. She almost screamed when he did, soul flashing brightly. 

Did she just-

No way…

She just came from him slipping one finger into her. 

Woah…

P E R F E C T L I T T L E M A T E 

Sans growled possessively. He’d get to see her cum many more times tonight. He couldn’t wait.  
He tentatively slid another finger into her, knowing that it was a “stretch”... heh… but heats made things that would normally hurt feel pleasurable to some extent, so he knew that she was probably ok. Especially when she keened and bucked her hips into his hand. 

Yeah. 

She was just fine.

Stars, she was so wet. He couldn’t wait to feel all of that dripping down his cock. 

Deciding that she was ready for another finger, he slid it in beside the first 2, making sure to scissor them a bit to stretch her out. It barely seemed to be working. She was so unbelievably tight. If he had been human, his fingers would have started going numb by now.

Sans started drooling again when he thought about how tight she would be around his huge… throbbing…

She whimpered in pain when he thrust his bones into her sensitive sex far too hard. He snapped out of his thoughts and lapped at her neck apologetically, purring softly to comfort her. 

He thought about slipping his pinky bone into her along with the others, but decided that it wouldn’t make much of a difference, and there was no way that he was going to fist her on their first fucking time together. He would just have to make her take his knot carefully. 

With that thought at the forefront of his mind, Sans removed his fingers, licking his mate’s  
D E L I C I O U S cream from his bones, and turned her over so she was on her hands and knees. Well, sort of. She was so shaky that she couldn’t hold herself up, so Sans wrapped an arm around her middle, pulling her hips up so her lower back was pressed against the curve of his big belly. He shuddered as he magicked away his clothes so he could finally feel her skin against all of him. 

Including his member. 

He was as long as his sweetheart’s forearm, and thick as a soda can at the base. For now, at least. The head was angular, and leaked red magic constantly. With this massive thing pressed against her soft little thigh, she suddenly was shocked into a moment of lucidity.

“Sans?” She whispered, trembling from her heat, and slurring from exhaustion, “Whas happenin?”

Sans chuckled darkly, bestial instincts completely overtaking his mind. 

“i’m claimin’ ya, sweetheart.”  
With that, he guided the head of his cock to her fluttering entrance, groaning as it seemed to kiss him. 

He pushed slightly, waiting for her slit to open up for him…

The head popped in, barely fitting. 

“SANS!” She screamed, writhing against his grip on her waist, which only tightened further as pleasure washed over him.

S U C H A G O O D L I T T L E G I R L

The heat seemed to overtake her quickly, finally given a glimpse of being satisfied by his thick cock breaching her trembling entrance. It was a good thing she was so wet, or it would have hurt a lot more. 

Sans was having a difficult time going slow, but he couldn’t exactly speed up. Her tight little walls were constricting him, preventing him from pushing forward at more than a snail’s pace. Slowly, so so slowly, he inched his cock into her, getting thicker and thicker with each millimeter. She was whining and clawing at the sheets in front of her, overwhelmed by the stretch. Sans couldn’t help but gloat a little.

“heh... never taken anything this thick before, have ya sweetcheeks?”

He only got a groan in response, but it was enough for him. He grinned ferally, and redoubled his efforts, pushing harder into her. 

After what felt like an eternity, he was almost completely inside of her, and Sans was ridiculously close to coming, just from sheathing himself. His tapered head was pressed insistantly against her cervix, as though it wanted to slip past it as well. Now, for monsters, this wouldn’t be a problem, as they could just make their magic open up-

Her cervix relaxed and the thick head of his cock slipped past it and Sans almost lost it. He was completely sheathed in her little tunnel, his knot forming alarmingly fast. He pulled away to sit up so he wasn’t covering her body with his and squeezed the base of his meat to stop himself from coming so quickly. While doing so, he was met with the lovely view of her stretched so fucking  
T I G H T L Y around him. 

Sans lost it.

He grabbed his mate’s hips and began rutting into her, unable to register her shrieks of discomfort. Unable to think of anything but fucking her into the next timeline. 

And Sans fucked H A R D. 

He was sure that he left bruises on her little hips as he snapped her back to take his girth again and again and again and again.

She was wailing, but he could barely hear her over the ringing in his ears and the voice in his head demanding that he C L A I M H E R. 

As his knot started to form, popping in and out of her painfully, Sans roared, leaned forward and sank his sharp teeth into her shoulder. At the same time, he shoved his hips forward one last time, plunging his far too thick knot into her sensitive little core. 

As the knot locked him in place, the head of his cock twitching and trapped in the opening of his mate’s womb, Sans came. 

Harder than he ever had in his life. 

His magic P O U R E D into her, unable to slip past the tight seal of her cervix, and even if it did, there was no way it could make it past his knot. 

Sans savored the taste of her blood on his tongue, and placed a skeletal hand over her belly to feel when the swelling started. He would be locked in her for hours and in that time, she would be left to fill up with all the magic that that his big balls could give her. 

She was whimpering and squirming, likely from the flood of hot monster seed that was filling her womb. Sans sighed, soul happy to have been able to give his mate what she needed as he rolled them both so he was sitting up against her headboard and she was knotted on his lap. 

It was this familiar position, the one that had always made her feel so safe with him, pressed back against the big belly that she said, giggling, made him like, “a giant warm pillow” that snapped Sans out of his beastial daze. 

Oh stars.

No.

No no no no N O N O N O N O

N O.

He had taken her without a thought about what she would feel when her heat was over.

He had essentially raped his soulmate. 

Fuck, stars N O. 

The moment when his little one told him, sobbing into his jacket, about her ex who had forced himself on her flashed behind his eyes. 

He was no better.

He really was a monster.

He felt his soul cracking in panic as he looked down at the state that his mate was in for the first time and almost started sobbing. 

She was covered in bruises. Her hips were so dark with them that they almost looked like shadows underneath her skin. Her shoulder where he had bitten her looked terribly painful and was leaking a steady stream of blood. He instinctually started lapping at the wound, saliva mixing with his tears as his magic worked to stop the bleeding. She had gone limp in his grasp, and Sans wasn’t sure if she had fainted, or was too exhausted to lift her head. 

For the first time in his life, Sans cursed the existence of his knot. He couldn’t take care of her properly while he was still locked inside of her. Fucking biology. 

After a moment, his little mate began to stir, and dread mixed with hope filled him. It was a strange combination. 

Eventually, the dread won out as when she woke up... his sweetheart began to cry. 

“oh stars, baby.” Sans whispered, soul wrenching inside of his chest. 

He pulled her closer against him, cradling her the best he could, and nuzzled his face into the crook of her neck, rocking her slowly. 

Her quiet sobs were so heartbreaking, that Sans couldn’t help but cry with her. 

“It- it hurts, Sans!” She whimpered.

He knew, oh stars he knew. His soul was pulsing with sympathy for his mate’s pain, demanding that he take it away. But how could he take it away when he was the source? 

He wrapped an arm around her belly to try to draw her closer, but recoiled when she yelped. Her little tummy had swelled a bit from all the magic that he had pumped into it, and pressing it had squished the hot fluid around inside of her.  
“i know, baby, i know.” Sans managed to choke out into her neck, placing a hand over her swollen womb and rubbing very gently. He never thought he would hate feeling the bulge of his cock through his mate’s skin, but there he was. 

“I didn’t-” She sobbed brokenly, “I want it out, Sans. Please!” 

Sans closed his eyes at the request, knowing that he couldn’t do what she asked. 

“I’m so sorry, hunny, but we have ta wait a bit.” 

It was going to take quite a while for his knot to go down, even when his magic was thrumming with discomfort for his crying mate. Sans spent the next hour cuddling with her as best he could, muttering in her ear that she was safe and he wouldn’t let anything hurt her ever again. Eventually, her sobs died out into quiet little hiccups, which almost broke his heart more. 

Finally, Sans felt his knot start to get smaller. He almost collapsed in relief. Once it was out of her, he could make everything better. 

There was an itching thought in the back of his mind that said that he could lose her forever, that this mistake could cost him his mate, but he pushed it down violently. 

The knot was small enough that he could start to pull out, but he wanted to warn her first. 

 

“a’right baby girl, i’mma take it out now, ok? it might hurt a little though, so just hold on ta me.”

She nodded, and he placed his hands on her hips to lift her off, when he remembered her bruises and decided to put her on all fours again. The squeek of fear that left her lips as he did so made him flinch, but he placed one hand on her belly, and the other on her thigh, and began to pull out. 

As soon as his head was removed from her womb, his seed began to flood out of her, leaking furiously around his softening member. She whimpered as his cock dragged across her bruised walls, but held onto his arm around her middle like he told her to. 

When he was completely out of her, he wasted no time in sweeping her up into his arms and carrying her to her bathroom, which had a big bathtub. Sans remembered teasing her about the tub and asking why she wouldn’t rather just shower. She just laughed and said that she couldn’t play with her rubber ducks in a shower. Sans was thankful for the bath now.

He turned on the faucet and checked the temperature to make sure it wasn’t too hot or too cold. While he waited for the tub to fill, he held her on his lap, letting her cling to him. 

Her soul was trembling in confusion. Sans was her soulmate. Why had he hurt her like this? Was it a mistake? He would never want to hurt her, ever. It must have been a mistake. 

In a few minutes, the tub had filled with warm water and Sans gently placed her into it, then reached under her sink to pull out a wash cloth and some soap. He cleaned between her legs gingerly, knowing that she would rather do it herself, but also knowing that she really couldn’t right now. 

“Why?” A soft voice asked.

He looked into her eyes for the first time and it almost broke him. She was crushed by what he’d done. 

“your heat.” He said simply. 

“My- my what?” She asked, tilting her head in that adorable way.

Sans sighed, “i think bein’ around a monster made ya go into heat.” 

Stars, how could he explain what he had done to her when she was looking at him like that?

“ya texted me wantin’ help, and when i came, i could just smell ya, sweetheart.” 

Her eyes were big and… trusting… she believed him so far. 

“it made me go crazy. every instinct in me sayin’ i needed to help ya.” 

Sans swallowed thickly, remembering the moment of lucidity you had had when he was just about to take you. 

“i’m so sorry, baby girl. i never meant to hurt ya.”

She was crying again and the sight killed him, but suddenly, she flung her arms around his neck and sobbed into his ribcage. This all had been too much for her. She couldn’t process everything that had happened, but she trusted Sans with everything in her and KNEW that he would never intentionally hurt her. He wasn’t her ex. Not even close. 

Sans was clinging to her like she was his lifeline. Honestly, she kind of was. He lifted her from the bathwater when she was clean and dried her off with a big fluffy towel, then teleported them both into his room in the apartment he shared with Papyrus. He carefully wrapped his favorite hoodie around her, wincing whenever he caught sight of her bruised hips, and pulled her into bed. 

Sans cuddled his mate closer than ever before, making full use of his “giant warm pillow” and sighed with relief that she was ok. She was safe. That’s all he could ever ask for.


	2. Reconciliation

**Summary for the Chapter:**

> The next morning

**Notes for the Chapter:**

> Soooo yeah, a lot of people wanted me to write another chapter. As per usual, at 1 in the morning the inspiration decided to hit me! I hope you all like it! :)

That night, Sans dreamt of his sweetheart. He dreamt of the day that they had gone to a local candy shop and he had let her pick out whatever she wanted. She had run around like… like a human in a candy shop, until she had a small bag of different flavors and types. She looked longingly at another display, but she was always afraid of being a burden on her mate, so she reluctantly turned away. 

Sans would have none of it. He grabbed another bag and filled it almost to bursting with the candy that his little one had been looking at, ignoring her protests, and bought that and her own selection. 

As they left the shop, Sans insisting on carrying the bags, his sweetheart looked up at him and asked, with loving, yet serious eyes, “What did I ever do to deserve you, Sans?”

Sans grinned and replied, “tibia honest, i’m the numbskull who doesn’t deserve you, baby.”

She giggled and shoved him, not moving him at all. 

It had started to snow as they walked home. It was so peaceful.

Sans woke up. 

For one glorious moment, he didn’t remember. He looked down at his little mate, surprised to find her cuddled against him as he slept, practically swimming in his oversized hoodie, too. He smiled softly down at her, enjoying her closeness. She had never slept in his bed before, what-

Oh stars. 

Oh N O. 

His soul ached in his chest once more as he remembered the previous day. Receiving a distressed text from his mate, finding her strangely in heat, then…  
Sans shuddered as he recalled what he had done to her. How he had HURT her. 

That could have been a nightmare, couldn’t it? He didn’t actually hurt his precious, fragile little mate… 

Did he?

One inhale told him all he needed to know. He smelled dried blood on her, mixed sickeningly with the stench of fear and pain. Apparently, the little soak in the bath last night hadn’t washed away all the evidence of Sans’s actions. 

Sans actually whimpered as he realized that yes, he had indeed violated his mate’s trust and body, hurting her in the worst possible way. What was he going to do? She would wake up and realize that he was a monster in more ways than one and L E A V E H I M. 

No… he couldn’t let that happen.

But… maybe she would be safer if she left.

N O. 

She was safest with him. Wrapped in his arms and warm and safe and cared for. Nothing would E V E R hurt her again. 

But he had been the one to hurt her. How could he protect her from himself?

Sans’s internal struggle was interrupted by his little one stirring softly. She shifted, scrunching her eyes as she stretched. He could barely see her moving, the hoodie was so big on her. He didn’t, however, miss the pained whine from her throat and the wince on her face as she stretched her sore muscles and registered pain in many other places. 

Worried and desperate to fix what he had done, Sans rolled so he was on top of her and looking deep into her eyes. He inhaled again to smell where she was hurting most. 

As she looked up at him, unable to miss the concern in his gaze, he saw confusion for a second.

“Sans, why am I so sore-”

Then she froze. Sans saw the exact moment when she must also have remembered, although what she remembered, he wasn’t sure. Heats could make memories a bit fuzzy. He did know that she must at least remember coming to with a massive monster cock plugging up her womb with hot seed and her mate practically crying, panicked, into her shoulder. 

He saw her throat bulge for an instant as she swallowed thickly. Sans waited with bated breath for how she would react to her memories. 

Please don’t cry. Stars, he couldn’t handle it when she cried.

What she actually did was much different than he expected.

Her gaze hardened and her nostrils flared as every muscle in her body stiffened until Sans could practically feel the anger pouring off of her. 

“Explain. Now.”

Well, then. 

That was unexpected.

Didn’t she cling to him and forgive him the night before? She seemed to just want him to hold her after everything had happened. She didn’t seem to bear him ill will for what he’d done. Why the change of heart?

Oh wait.

She hadn’t said she forgave him. She had probably been too exhausted to truly realize what he’s done. 

Sans was used to being the big bad monster in the relationship, but he could actually feel his soul cowering before her. 

Good. He deserved it.

“i got ya text and-” he started to repeat. 

“Yeah, I remember what you said, Sans. I want you to explain what made you think it was ok to RAPE me.” she snarled, glaring up at him. 

Sans recoiled at that, face crumpling in revulsion. It was the truth, though. How was he supposed to defend himself? Should he even?

His soul was whining, wanting to make all of this better, wanting to take away all her pain. Not knowing what else he was supposed to do, he gave in and tried to fix the closest source of pain. His tongue snaked out and gently lapped at the wound that his teeth had made on her shoulder the night before. His previous ministrations had made it scab over, but it was still red and angry. 

“DON’T TOUCH ME!” His mate shrieked.

Sans practically vaulted away from her, falling off the bed in the process and landing on his tailbone. His soul felt like it was exploding in his chest and he was unable to rise. He moaned in pain and clutched at his ribcage, head lowering as though in submission. 

It was then that she started to cry, curling up with her knees to her chest and if her tears weren’t enough to break him, her next words, choked out through gasping breaths, were. 

“I- I thought you loved me. Why would you hu-hurt me like that? Why? Why?” 

Sans, his soul unable to stand the notion of his mate doubting his love for her, managed to sit up on his knees and grasp onto the edge of the bed, burying his face into it as he sobbed with her. 

After a while, neither of them knew how long, they both ran out of tears to cry and they just sat in silence. Her bundled in his huge hoodie on the bed, him kneeling on the floor as close to her as he dared. 

Sans managed to croak out, “i do love ya, sweetheart.” 

She hiccupped and whispered, “Then why?”

He knew what she was really trying to ask. ‘After what I told you about my ex, why would you do the exact same thing as him if you love me?’

He closed his eyes, bowing his head once again. 

“i saw ya there on your bed, and i was just gonna check ta see if you were ok, but…” 

Despite Sans’s previous assumption that he had cried all of his tears, more started to leak from the corners of his eye sockets. 

“i lost control. i know that’s not an excuse, but i need you to know that i would never hurt you on purpose, baby.” Sans felt his soul tremble in pain. “N E V E R.” 

“stars, sweetheart, my soul cracked when i came back to myself and saw what I did.”

Almost subconsciously, his mate’s head jerked to look at him, concern for her soulmate bubbling up in her despite herself. “It did?” She asked quietly.

Slowly, so as not to startle his mate, Sans pulled his soul from his chest and held it out for her to see.  
Drawn by her natural graviation to her soulmate, she let herself crawl across the bed towards him to get a better look, noticing just how much she was hurting between her legs.

Sans hadn’t been lying. His soul, shining white as was normal for a monster apart from some scarring that had occured in the Underground, had a new, deep crack right down the center. Her breath caught in her throat as she looked at it, her own soul aching for the pain that he must have been in for this level of damage to have happened. 

She knew then that he had been telling the truth about a lot of things. He wasn’t making excuses, he wasn’t trying to make what he did disappear, he truly hadn’t meant to hurt her. His soul wouldn’t have cracked if he had. 

Slowly, she reached her hand forward and took his soul from his hand, noticing how he shivered when she touched it. She brought it to her lips and placed a gentle kiss right over the crack. 

Sans couldn’t stop himself. His hands reached out, gripping her thighs tenderly, and pulled her towards him so she was sitting on the edge of the bed. He was knelt between her thighs, burying his face into her stomach, hands wrapped desperately around her waist. 

He inhaled deeply, knowing his soul was throbbing painfully in her hands as his heightened senses registered how sore her little womb and tunnel were from being stretched so cruelly. His tongue formed in his mouth, and he wanted to run it over every little inch of her that he had caused to be in pain, but he knew that he was on thin ice as it was. 

One of her little hands rested on his skull, the other holding his soul. He was completely at her mercy. She could crush him, the big bad monster, if she wanted to. 

But she didn’t. Instead, she stroked his skull and cooed softly that it was ok, that she was ok. 

HE should have been the one comforting HER. 

This was his fault, after all.

He had probably caused her heat, and had certainly acted like a mindless animal, all instinct and no higher brain function. But with his little one touching him so tenderly and treating him with such love, he could barely think about what he had done. 

She allowed his soul to return to his chest, shifting her legs a bit while doing so and Sans suddenly smelled blood. 

B L O O D

His knot must have torn her walls when he forced it into her, and the wound was reopening. 

“fuck, baby.” Sans cursed, nuzzling his skull into her belly, right over her sore womb, not sure what else to do, “you must be hurtin’ so bad right now.” 

She sniffled a little, but nodded. 

Sans growled as the scent of blood grew stronger. She was still naked under his hoodie, and normally, the sight would have been arousing as all hell, but right now, the lack of clothes made it all the easier for him to smell that his mate was in P A I N. 

“sweetheart... hunny, you’re bleedin’.” Sans managed to gasp into the fabric of his hoodie. 

“I am?” She asked, although Sans had a feeling that she wasn’t really surprised. 

“yeah, fuck i can smell it. i can feel it hurtin’ ya, baby.” He looked up at her, a tinge of panic in his expression. “let me help, sweety, i promise i won’t hurt ya again.”

Sans was flat out begging, now. 

“please, baby, i will never let anything hurt ya. i need to fix this, please. i’m so sorry for doin’ this to ya, hunny. i love ya so much. please let me help, please baby.” 

Seeing this giant of a monster pleading with her to let him help made her soul clench and, reluctantly, she agreed. She didn’t know what he was going to do, but if it made this terrible pain between her legs go away, she was open to almost anything. 

That is, until Sans, relieved by her assent, eagerly spread her legs wide and pushed the hem of his hoodie up over her hips to expose her, apparently bleeding, core. 

She yelped, recoiling a little, and Sans rested his head on one of her thighs, pleas pouring from his mouth again. 

“please, sweetheart, i know ya scared, but i won’t hurt ya, I P R O M I S E.” the last words resonated in her soul. 

She took a deep breath, reminding herself that this was SANS, not her ex. Her Sans loved her, he wouldn’t hurt her again. It was an accident. 

She opened her legs wider, paling from mortification that she was actually letting her mate do this. 

Sans made sure to move slower this time as he spread her legs a little more, just enough for his big skull to fit between them. With every inhale, he was overwhelmed by the smell of her blood and it took everything in him not to slather her in his magic immediately. He needed her to be comfortable with this. 

Slowly, he allowed his glowing red tongue to snake out of his mouth and taste the air near her sex. Then, he very gently touched her outer lips with it. 

She jumped, more from surprise than actual fear, although he could smell a lot more of that unwanted scent than he wanted. Making sure to keep still against her for a few moments, Sans just breathed gently on her sweet little lips. Then, he slowly moved his tongue so it parted her pink folds, finally, and unfortunately, tasting the blood that had begun to leak from her. 

Sans repressed a growl, knowing that would startle his mate, and gently caressed her opening with his glowing appendage. She was so tender there that she had to bite her hand to keep from whimpering. However, as soon as his magic touched where she was hurting, it started to hurt less and less. Shocked that he could heal her so effectively, she stared down at him in wonder.

Sans, having done pretty much all he could to heal her entrance, began to gently slip his tongue into her. He winced as he heard her cry out, but she didn’t recoil, she gripped his skull with shaking hands. The taste of blood was almost overwhelming and this time, he couldn’t repress his growl, the sound shaking through her in a surprisingly pleasant way. He had found where he tore her, and his magic was working quickly to heal it, but her walls were still bruised and damaged.

As he slid his tongue deeper and deeper into her, she began to whimper more from relief than pain. 

His tongue was warm and soft, squishy like Sans’s belly that she loved so much. It didn’t stretch her out or make her hurt, but it filled her up in a way that made her feel weirdly safe. It was like getting a hug from the inside, especially with the way that it tingled whenever it found a sore spot. 

Thank the stars for magic that he could make his tongue as long as he wanted. Finally, he was far enough inside of her that he could feel the tip kissing her cervix. It was swollen and ached horribly from the punishment that it had endured. He could actually taste some of his seed that hadn’t leaked out of her and almost snarled in self-hatred. 

He knew he couldn’t reach her sore little womb, and that broke his heart. He hated leaving any part of her uncared for, but he wasn’t about to force his way past her cervix again, healing magic or not. So, he contented himself with sweet little laps of his tongue against the tiny doorway, making sure to clean off any of his essence that was left over, and made sure to spread his saliva thickly over her to take away the ache. 

Her grip on his skull tightened as he began to pull out from her, spreading his magic liberally over every inch as he went. That was about the best he could do for her little slit. The magic would heal her over the next few hours. 

As he withdrew from her, he looked up into his mate’s eyes, delighted to find that there was very little fear left in her gaze. Finally, he pulled away altogether, sitting up a little straighter as he realized that there was more healing to be done. Gently, he lifted the hem of the hoodie higher to expose her hips to his gaze. He winced. The night before, they had looked dark with bruising, but now, he saw just how extensive the bruises were. He could clearly see where his bones had dug into her skin far too harshly, leaving black and blue handprints that were ringed with red. 

He lapped at these marks tenderly, watching as they turned from black, to purple, to a light green. Sans pulled away, then, looking up at her to make sure she was ok. 

There were tears in her eyes. 

Fuck.

Immediately, he stood, lifting his mate by her newly healed hips to be cuddled against his chest, her abdomen pressed against his big belly and her legs wrapped around his hips. He crooned soft comforts in her ear. Letting her know that he was there and she was safe. 

“are you ok, baby?” Sans asked gently, always concerned whenever there were tears in his mate’s eyes. He hoped to all the stars that he hadn’t been too rough with her. 

“Yeah, I’m ok, Sans.” She whispered into his shoulder, “I just really love you.”

Sans felt his soul C L E N C H. She loved him. After everything, she still loved him. 

“i love you too, sweetheart.” Sans rumbled, “don’t know what i did ta deserve you.”

 

Epilogue

“Sans, can we go get some food? I haven’t eaten in like a day and a half.”

……...

“yeah, we’re gonna have ta fix that.”

**Notes for the Chapter:**

> Please leave me a comment if you liked it. I really appreciated everyone who asked for this chapter. <3


	3. Author's Note

So, after writing this work, I realized that I have about 80,000 other ideas for stories in Undertale and other fandoms. If any of you want to see more from me, please feel free to leave suggestions in the comments. I find writing very therapeutic, and can get chapters out pretty quickly because once I grasp onto an idea, my brain just frickin' explodes and I can't stop writing for hours. Please leave a comment letting me know if you want more of this type of story with Sans and a Reader, or if you want something else! If I don't know the fandom that you request, I apologize. 

 

Love you guys, and thanks for reading! <3

**Author's Note:**

> I really enjoyed writing this. I have such a soft spot for gentle giants who are super protective of their mates, so this has been in my head for a while. Please let me know if you liked it!


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